1. Field of the Invention
This invention relates generally to the field of enhanced oil production and recovery. More specifically, the invention relates to the field of recovery of crude oil from produced emulsions of surfactant-polymer enhanced oil recovery floods. The invention has particular relevance to the use of cationic surfactants and amphoteric surfactants to enhance oil production and recovery from these emulsions.
2. Background of the Invention
The production of crude oil from reservoirs typically results in significant quantities of non-produced crude oil remaining in the reservoir. Methods for recovering the crude oil include primary production and secondary water flooding. Several methods at various stages of development and application offer promise of recovering significant amounts of oil remaining after conventional production. Such methods include surfactant-polymer and alkali-surfactant-polymer enhanced oil recovery floods, which involve injecting combinations of these materials in brine solutions into the reservoir. Results of such methods include a produced emulsion that typically contains crude oil, water, surfactant, polymer, and alkali when used. Drawbacks include difficulties in separating the emulsion into clean water and dry oil for sale of the crude oil and proper disposal of the water in an environmentally safe manner. Moreover, demulsifiers used to separate conventional oilfield emulsions may be ineffective for some emulsions from surfactant-polymer and alkali-surfactant-polymer processes. Various experiments have shown that conventional nonionic demulsifiers may not be able to provide the desired separation for these processes. For instance, they may fail to produce water with a sufficiently low content of oil.
Consequently, there is a need for improved methods in separating the crude oil and water of the emulsions from surfactant-polymer and alkali-surfactant-polymer processes. Additional needs include improved methods for demulsifying the produced emulsion to produce a clean separation of the crude oil and water.